The present invention relates to a power source arrangement for wire-cut, electric discharge machining which provides for increased cutting speed during wire-cut, electric discharge machining.
In wire-cut, electric discharge machining, for example, as shown in FIG. 1, a transistor 3 is controlled to be turned ON and OFF by pulses from a pulse generator 4 and, when the transistor 3 is in the ON state, a capacitor 5 is charged via a resistor 2 from a DC power source 1 and then the charged voltage of the capacitor 5 is applied across a wire electrode 7 and a workpiece 6, thereby performing electric discharge machining. Reference numeral 8 indicates a contactor, and 9 and 10 designate guides.
The voltage across the wire electrode 7 and the workpiece 6, that is, the gap voltage undergoes such variations, for instance, as shown in FIG. 2. That is to say, discharge occurs after or during charging of the capacitor 5. Experimental results have revealed that the cutting speed increases with a decrease in the charging voltage of the capacitor. The reason for this has not been made sufficiently clear yet, but it is said that, for example, if the capacitor charging voltage is high, the gap between the wire electrode and the workpiece is enlarged by electric discharge machining, making it difficult for a discharge produced at a point to shift to another point.
One might consider lowering the voltage of the DC power source 1 so as to make the charging voltage of the capacitor 5 lower, but this would reduce the charging energy of the capacitor 5, making it impossible to enhance the cutting speed. Also it would be possible to increase the value of the resistor 2, but this would also have the defects of lowered charging speed and increased power loss.